1. Field of the Invention
The present invention relates to an image forming apparatus such as an MFP (Multi-Functional Peripheral) and a technique related thereto.
2. Description of the Related Art
There is a technique for performing print output after a user logs in to an image forming apparatus, instead of immediately causing the image forming apparatus to execute print output, on the basis of print data which have been transmitted from a computer. Such technique will be referred to as a pull print technique (or authenticated print technique) (see Japanese Laid-Open Patent Publication No. 2010-3006 A). According to this technique, after a user moves from a location where the computer exists to a location where the image forming apparatus exists, the image forming apparatus performs print output, and therefore, a print output material which is output to a sheet discharge tray and the like of the image forming apparatus can be prevented from being seen by others.
Such techniques include a technique for using a server computer (which may also be simply referred to as a server). More specifically, first, a user UB operates a client computer to transmit data of a print target document (print data) to the server. In other words, the print data of a pull print job of the user UB of the client computer (which may also be simply referred to as an authenticated print job) are transmitted from the computer to the server, and the print data are temporarily stored in the server. At this occasion, print output processing based on the print data has not yet been performed. Thereafter, this time, user authentication operation is performed using an operation input unit and the like of the image forming apparatus, and then, the print data are retrieved (pulled) from the server, and the image forming apparatus performs print output (performs printing).
However, print systems include a system constituted by a plurality of MFPs without providing any server. Such system is also referred to as a server-less print system (or a server-less ubiquitous system) and the like.
Such server-less print system also performs pull print (see FIGS. 13 to 15). In the server-less print system, any given MFP 10a of multiple MFPs 10 (10a, 10b, . . . ) is configured to achieve the same function as the server.
The pull print performed by a certain user UB is done as follows, for example. First, as shown in FIG. 14, a pull print job (more specifically, box save command) of the user UB is transmitted from a computer 50 to the MFP 10a. Subsequently, as shown in FIG. 15, the user UB moves from the location where the computer 50 exists to the location where the MFP 10b exists, and the user UB operates the MFP 10b to try to cause the MFP 10b to print and output a document DZ of the pull print job. More specifically, the user UB logs in to the MFP 10b, and thereafter, the user UB tries to display a print candidate file list for the user UB.
In a normal state, the print candidate file list (list including storage target data (document DZ) that are stored by a storage job) is displayed, and the user UB selects the document file (document DZ) of the print target from among the print candidate file list, and gives a print output command. Then, in response to this print output command, a print output material based on the pull print job is printed and output by the MFP 10b. 
However, depending on the operation state of the MFP 10a which is the storage destination of the data of the pull print job, there would be a delay in displaying of the print candidate file list on the MFP 10b, and there may be a delay in the time point of finish of the data storage processing (accumulation processing) of the pull print job given by the user UB.
For example, as shown in FIG. 14, such situation would occur if the MFP 10a has already received a print output job from another user UA and the MFP 10a is executing the print output job thereof (a print output operation of a document DY) when the pull print job given by the user UB is transmitted from the computer 50 to the MFP 10a. FIG. 13 shows a case where the print output job was given by the user UA prior to the pull print job operation of FIG. 14, and the print output of the document DY has been started.
In this case, because the processing performance and the like of the MFP 10a are limited, and because, e.g., the hard disk drive (HDD) is already used in the print output operation of the MFP 10a, the MFP 10a cannot immediately store the data of the pull print job given by the computer 50 into the hard disk drive.
Therefore, as shown in FIG. 15, even if the MFP 10a receives a display request from the MFP 10b concerning the print candidate file list of the pull print jobs, the MFP 10a has not yet finished the data storage processing of the job data, and has not yet obtained the data for displaying the job list. Even if list information LT is replied from the MFP 10a to the MFP 10b at this occasion, the list information LT does not include information about the pull print job JB (e.g., information about the document file of the storage target in the storage job).
Therefore, the user UB cannot find the desired print target file (storage target document file) in the print candidate file list displayed by the MFP 10b, and the user UB is confused by being unable to find, in the list, the desired file of the pull print job JB, which the user UB believes to have transmitted to the computer 50. In particular, in many cases, the user UB cannot find that there is a delay due to a job of another user UA, and in many cases, the user UB cannot understand the situation. Then, after about a predetermined period of waiting time passes, the user UB is required to perform operation all over again from the login operation to the MFP 10b, and do display operation again to display the print candidate file list of the pull print jobs for the user UB. Therefore, sometimes, the user UB has no choice but to wait for a relatively long period of time.
As described above, because information for displaying the list cannot be obtained until the MFP 10a finishes the data storage processing of the job data, there is a problem in that it takes a pretty long time for the storage target data (document DZ) stored by the storage job of the pull print job JB to be displayed in the print candidate file list of another MFP 10b. 